Hydrocarbon Gas Processing

ABSTRACT

A process and an apparatus are disclosed for the recovery of ethane, ethylene, propane, propylene, and heavier hydrocarbon components from a hydrocarbon gas stream. The stream is cooled and divided into first and second streams. The first stream is further cooled to condense substantially all of it and is thereafter expanded to the fractionation tower pressure and supplied to the fractionation tower at an upper mid-column feed position. The second stream is expanded to the tower pressure and supplied to the column at a mid-column feed position. A distillation vapor stream is withdrawn from the column above the feed point of the first stream, combined with a portion of the tower overhead vapor stream, compressed to higher pressure, and directed into heat exchange relation with the remaining tower overhead vapor stream to cool the compressed combined vapor stream and condense at least a part of it, forming a condensed stream. At least a portion of the condensed stream is expanded to the tower pressure and directed to the fractionation tower as its top feed. The quantities and temperatures of the feeds to the fractionation tower are effective to maintain the overhead temperature of the fractionation tower at a temperature whereby the major portion of the desired components is recovered.

BACKGROUND OF THE INVENTION

This invention relates to a process and an apparatus for the separationof a gas containing hydrocarbons. The applicants claim the benefitsunder Title 35, United States Code, Section 119(e) of prior U.S.Provisional Applications No. 61/244,181 which was filed on Sep. 21,2009, No. 61/346,150 which was filed on May 19, 2010, and No. 61/351,045which was filed on Jun. 3, 2010.

Ethylene, ethane, propylene, propane, and/or heavier hydrocarbons can berecovered from a variety of gases, such as natural gas, refinery gas,and synthetic gas streams obtained from other hydrocarbon materials suchas coal, crude oil, naphtha, oil shale, tar sands, and lignite. Naturalgas usually has a major proportion of methane and ethane, i.e., methaneand ethane together comprise at least 50 mole percent of the gas. Thegas also contains relatively lesser amounts of heavier hydrocarbons suchas propane, butanes, pentanes, and the like, as well as hydrogen,nitrogen, carbon dioxide, and other gases.

The present invention is generally concerned with the recovery ofethylene, ethane, propylene, propane, and heavier hydrocarbons from suchgas streams. A typical analysis of a gas stream to be processed inaccordance with this invention would be, in approximate mole percent,88.1% methane, 6.0% ethane and other C₂ components, 2.5% propane andother C₃ components, 0.2% iso-butane, 0.2% normal butane, and 0.5%pentanes plus, with the balance made up of nitrogen and carbon dioxide.Sulfur containing gases are also sometimes present.

The historically cyclic fluctuations in the prices of both natural gasand its natural gas liquid (NGL) constituents have at times reduced theincremental value of ethane, ethylene, propane, propylene, and heaviercomponents as liquid products. This has resulted in a demand forprocesses that can provide more efficient recoveries of these products,for processes that can provide efficient recoveries with lower capitalinvestment, and for processes that can be easily adapted or adjusted tovary the recovery of a specific component over a broad range. Availableprocesses for separating these materials include those based uponcooling and refrigeration of gas, oil absorption, and refrigerated oilabsorption. Additionally, cryogenic processes have become popularbecause of the availability of economical equipment that produces powerwhile simultaneously expanding and extracting heat from the gas beingprocessed. Depending upon the pressure of the gas source, the richness(ethane, ethylene, and heavier hydrocarbons content) of the gas, and thedesired end products, each of these processes or a combination thereofmay be employed.

The cryogenic expansion process is now generally preferred for naturalgas liquids recovery because it provides maximum simplicity with ease ofstartup, operating flexibility, good efficiency, safety, and goodreliability. U.S. Pat. Nos. 3,292,380; 4,061,481; 4,140,504; 4,157,904;4,171,964; 4,185,978; 4,251,249; 4,278,457; 4,519,824; 4,617,039;4,687,499; 4,689,063; 4,690,702; 4,854,955; 4,869,740; 4,889,545;5,275,005; 5,555,748; 5,566,554; 5,568,737; 5,771,712; 5,799,507;5,881,569; 5,890,378; 5,983,664; 6,182,469; 6,578,379; 6,712,880;6,915,662; 7,191,617; 7,219,513; reissue U.S. Pat. No. 33,408; andco-pending application Ser. Nos. 11/430,412; 11/839,693; 11/971,491;12/206,230; 12/689,616; 12/717,394; 12/750,862; 12/772,472; and12/781,259 describe relevant processes (although the description of thepresent invention in some cases is based on different processingconditions than those described in the cited U.S. patents).

In a typical cryogenic expansion recovery process, a feed gas streamunder pressure is cooled by heat exchange with other streams of theprocess and/or external sources of refrigeration such as a propanecompression-refrigeration system. As the gas is cooled, liquids may becondensed and collected in one or more separators as high-pressureliquids containing some of the desired C₂+ components. Depending on therichness of the gas and the amount of liquids formed, the high-pressureliquids may be expanded to a lower pressure and fractionated. Thevaporization occurring during expansion of the liquids results infurther cooling of the stream. Under some conditions, pre-cooling thehigh pressure liquids prior to the expansion may be desirable in orderto further lower the temperature resulting from the expansion. Theexpanded stream, comprising a mixture of liquid and vapor, isfractionated in a distillation (demethanizer or deethanizer) column. Inthe column, the expansion cooled stream(s) is (are) distilled toseparate residual methane, nitrogen, and other volatile gases asoverhead vapor from the desired C₂ components, C₃ components, andheavier hydrocarbon components as bottom liquid product, or to separateresidual methane, C₂ components, nitrogen, and other volatile gases asoverhead vapor from the desired C₃ components and heavier hydrocarboncomponents as bottom liquid product.

If the feed gas is not totally condensed (typically it is not), thevapor remaining from the partial condensation can be split into twostreams. One portion of the vapor is passed through a work expansionmachine or engine, or an expansion valve, to a lower pressure at whichadditional liquids are condensed as a result of further cooling of thestream. The pressure after expansion is essentially the same as thepressure at which the distillation column is operated. The combinedvapor-liquid phases resulting from the expansion are supplied as feed tothe column.

The remaining portion of the vapor is cooled to substantial condensationby heat exchange with other process streams, e.g., the coldfractionation tower overhead. Some or all of the high-pressure liquidmay be combined with this vapor portion prior to cooling. The resultingcooled stream is then expanded through an appropriate expansion device,such as an expansion valve, to the pressure at which the demethanizer isoperated. During expansion, a portion of the liquid will vaporize,resulting in cooling of the total stream. The flash expanded stream isthen supplied as top feed to the demethanizer. Typically, the vaporportion of the flash expanded stream and the demethanizer overhead vaporcombine in an upper separator section in the fractionation tower asresidual methane product gas. Alternatively, the cooled and expandedstream may be supplied to a separator to provide vapor and liquidstreams. The vapor is combined with the tower overhead and the liquid issupplied to the column as a top column feed.

In the ideal operation of such a separation process, the residue gasleaving the process will contain substantially all of the methane in thefeed gas with essentially none of the heavier hydrocarbon components,and the bottoms fraction leaving the demethanizer will containsubstantially all of the heavier hydrocarbon components with essentiallyno methane or more volatile components. In practice, however, this idealsituation is not obtained because the conventional demethanizer isoperated largely as a stripping column. The methane product of theprocess, therefore, typically comprises vapors leaving the topfractionation stage of the column, together with vapors not subjected toany rectification step. Considerable losses of C₂, C₃, and C₄+components occur because the top liquid feed contains substantialquantities of these components and heavier hydrocarbon components,resulting in corresponding equilibrium quantities of C₂ components, C₃components, C₄ components, and heavier hydrocarbon components in thevapors leaving the top fractionation stage of the demethanizer. The lossof these desirable components could be significantly reduced if therising vapors could be brought into contact with a significant quantityof liquid (reflux) capable of absorbing the C₂ components, C₃components, C₄ components, and heavier hydrocarbon components from thevapors.

In recent years, the preferred processes for hydrocarbon separation usean upper absorber section to provide additional rectification of therising vapors. The source of the reflux stream for the upperrectification section is typically a recycled stream of residue gassupplied under pressure. The recycled residue gas stream is usuallycooled to substantial condensation by heat exchange with other processstreams, e.g., the cold fractionation tower overhead. The resultingsubstantially condensed stream is then expanded through an appropriateexpansion device, such as an expansion valve, to the pressure at whichthe demethanizer is operated. During expansion, a portion of the liquidwill usually vaporize, resulting in cooling of the total stream. Theflash expanded stream is then supplied as top feed to the demethanizer.Typically, the vapor portion of the expanded stream and the demethanizeroverhead vapor combine in an upper separator section in thefractionation tower as residual methane product gas. Alternatively, thecooled and expanded stream may be supplied to a separator to providevapor and liquid streams, so that thereafter the vapor is combined withthe tower overhead and the liquid is supplied to the column as a topcolumn feed. Typical process schemes of this type are disclosed in U.S.Pat. Nos. 4,889,545; 5,568,737; and 5,881,569; assignee's co-pendingapplication Ser. No. 12/717,394; and in Mowrey, E. Ross, “Efficient,High Recovery of Liquids from Natural Gas Utilizing a High PressureAbsorber”, Proceedings of the Eighty-First Annual Convention of the GasProcessors Association, Dallas, Tex., Mar. 11-13, 2002. These processesuse a compressor to provide the motive force for recycling the refluxstream to the demethanizer, adding to both the capital cost and theoperating cost of facilities using these processes.

The present invention also employs an upper rectification section (or aseparate rectification column if plant size or other factors favor usingseparate rectification and stripping columns). However, the refluxstream for this rectification section is provided by using a side drawof the vapors rising in a lower portion of the tower combined with aportion of the column overhead vapor. Because of the relatively highconcentration of C₂ components in the vapors lower in the tower, asignificant quantity of liquid can be condensed from this combined vaporstream with only a modest elevation in pressure, often using only therefrigeration available in the remaining portion of the cold overheadvapor leaving the upper rectification section of the column. Thiscondensed liquid, which is predominantly liquid methane, can then beused to absorb C₂ components, C₃ components, C₄ components, and heavierhydrocarbon components from the vapors rising through the upperrectification section and thereby capture these valuable components inthe bottom liquid product from the demethanizer.

Heretofore, compressing either a portion of the cold overhead vaporstream or compressing a side draw vapor stream to provide reflux for theupper rectification section of the column has been employed in C₂+recovery systems, as illustrated in assignee's U.S. Pat. No. 4,889,545and assignee's co-pending application Ser. No. 11/839,693, respectively.Surprisingly, applicants have found that combining a portion of the coldoverhead vapor with the side draw vapor stream and then compressing thecombined stream improves the system efficiency while reducing operatingcost.

In accordance with the present invention, it has been found that C₂recovery in excess of 95% and C₃ and C₄+ recoveries in excess of 99% canbe obtained. In addition, the present invention makes possibleessentially 100% separation of methane and lighter components from theC₂ components and heavier components at lower energy requirementscompared to the prior art while maintaining the recovery levels. Thepresent invention, although applicable at lower pressures and warmertemperatures, is particularly advantageous when processing feed gases inthe range of 400 to 1500 psia [2,758 to 10,342 kPa(a)] or higher underconditions requiring NGL recovery column overhead temperatures of −50°F. [−46° C.] or colder.

For a better understanding of the present invention, reference is madeto the following examples and drawings. Referring to the drawings:

FIG. 1 is a flow diagram of a prior art natural gas processing plant inaccordance with U.S. Pat. No. 4,889,545;

FIG. 2 is a flow diagram of a natural gas processing plant in accordancewith the present invention; and

FIGS. 3 through 6 are flow diagrams illustrating alternative means ofapplication of the present invention to a natural gas stream.

In the following explanation of the above figures, tables are providedsummarizing flow rates calculated for representative process conditions.In the tables appearing herein, the values for flow rates (in moles perhour) have been rounded to the nearest whole number for convenience. Thetotal stream rates shown in the tables include all non-hydrocarboncomponents and hence are generally larger than the sum of the streamflow rates for the hydrocarbon components. Temperatures indicated areapproximate values rounded to the nearest degree. It should also benoted that the process design calculations performed for the purpose ofcomparing the processes depicted in the figures are based on theassumption of no heat leak from (or to) the surroundings to (or from)the process. The quality of commercially available insulating materialsmakes this a very reasonable assumption and one that is typically madeby those skilled in the art.

For convenience, process parameters are reported in both the traditionalBritish units and in the units of the Système International d'Unités(SI). The molar flow rates given in the tables may be interpreted aseither pound moles per hour or kilogram moles per hour. The energyconsumptions reported as horsepower (HP) and/or thousand British ThermalUnits per hour (MBTU/Hr) correspond to the stated molar flow rates inpound moles per hour. The energy consumptions reported as kilowatts (kW)correspond to the stated molar flow rates in kilogram moles per hour.

DESCRIPTION OF THE PRIOR ART

FIG. 1 is a process flow diagram showing the design of a processingplant to recover C₂+ components from natural gas using prior artaccording to U.S. Pat. No. 4,889,545. In this simulation of the process,inlet gas enters the plant at 120° F. [49° C.] and 1040 psia [7,171kPa(a)] as stream 31. If the inlet gas contains a concentration ofsulfur compounds which would prevent the product streams from meetingspecifications, the sulfur compounds are removed by appropriatepretreatment of the feed gas (not illustrated). In addition, the feedstream is usually dehydrated to prevent hydrate (ice) formation undercryogenic conditions. Solid desiccant has typically been used for thispurpose.

The feed stream 31 is cooled in heat exchanger 10 by heat exchange withcool residue gas (stream 43 a), liquid product at 72° F. [22° C.](stream 42 a), demethanizer reboiler liquids at 52° F. [11° C.] (stream41), and demethanizer side reboiler liquids at −20° F. [−29° C.] (stream40). Note that in all cases exchanger 10 is representative of either amultitude of individual heat exchangers or a single multi-pass heatexchanger, or any combination thereof. (The decision as to whether touse more than one heat exchanger for the indicated cooling services willdepend on a number of factors including, but not limited to, inlet gasflow rate, heat exchanger size, stream temperatures, etc.) The cooledstream 31 a enters separator 11 at −18° F. [−28° C.] and 1025 psia[7,067 kPa(a)] where the vapor (stream 32) is separated from thecondensed liquid (stream 33). The separator liquid (stream 33) isexpanded to the operating pressure (approximately 392 psia [2,701kPa(a)]) of fractionation tower 17 by expansion valve 16, cooling stream33 a to −53° F. [−47° C.] before it is supplied to fractionation tower17 at a lower mid-column feed point.

The vapor (stream 32) from separator 11 is divided into two streams, 36and 37. Stream 36, containing about 38% of the total vapor, passesthrough heat exchanger 12 in heat exchange relation with the coldresidue gas (stream 43) where it is cooled to substantial condensation.The resulting substantially condensed stream 36 a at −142° F. [−96° C.]is then flash expanded through expansion valve 13 to slightly above theoperating pressure of fractionation tower 17. During expansion a portionof the stream is vaporized, resulting in cooling of the total stream. Inthe process illustrated in FIG. 1, the expanded stream 36 b leavingexpansion valve 13 reaches a temperature of −144° F. [−98° C.]. Theexpanded stream 36 b is warmed to −139° F. [−95° C.] and furthervaporized in heat exchanger 22 as it provides cooling and condensationof compressed recycle stream 44 a (described later in paragraph [0026]).The warmed stream 36 c is then supplied at an upper mid-column feedpoint, in absorbing section 17 a of fractionation tower 17.

The remaining 62% of the vapor from separator 11 (stream 37) enters awork expansion machine 14 in which mechanical energy is extracted fromthis portion of the high pressure feed. The machine 14 expands the vaporsubstantially isentropically to the tower operating pressure, with thework expansion cooling the expanded stream 37 a to a temperature ofapproximately −94° F. [−70° C.]. The typical commercially availableexpanders are capable of recovering on the order of 80-85% of the worktheoretically available in an ideal isentropic expansion. The workrecovered is often used to drive a centrifugal compressor (such as item15) that can be used to re-compress the residue gas (stream 43 b), forexample. The partially condensed expanded stream 37 a is thereaftersupplied as feed to fractionation tower 17 at a mid-column feed point.

The demethanizer in tower 17 is a conventional distillation columncontaining a plurality of vertically spaced trays, one or more packedbeds, or some combination of trays and packing. The demethanizer towerconsists of two sections: an upper absorbing (rectification) section 17a that contains the trays and/or packing to provide the necessarycontact between the vapor portions of the expanded streams 36 c and 37 arising upward and cold liquid falling downward to condense and absorbthe C₂ components, C₃ components, and heavier components; and a lower,stripping section 17 b that contains the trays and/or packing to providethe necessary contact between the liquids falling downward and thevapors rising upward. The demethanizing section 17 b also includes oneor more reboilers (such as the reboiler and side reboiler describedpreviously) which heat and vaporize a portion of the liquids flowingdown the column to provide the stripping vapors which flow up the columnto strip the liquid product, stream 42, of methane and lightercomponents. Stream 37 a enters demethanizer 17 at an intermediate feedposition located in the lower region of absorbing section 17 a ofdemethanizer 17. The liquid portion of the expanded stream 37 acommingles with liquids falling downward from absorbing section 17 a andthe combined liquid continues downward into stripping section 17 b ofdemethanizer 17. The vapor portion of the expanded stream 37 a risesupward through absorbing section 17 a and is contacted with cold liquidfalling downward to condense and absorb the C₂ components, C₃components, and heavier components.

In stripping section 17 b of demethanizer 17, the feed streams arestripped of their methane and lighter components. The resulting liquidproduct (stream 42) exits the bottom of tower 17 at 67° F. [19° C.](based on a typical specification of a methane to ethane ratio of0.015:1 on a volume basis in the bottom product) and is pumped to heatexchanger 10 by pump 20 to be heated to 116° F. [47° C.] as it providescooling to the feed gas as described earlier.

Cold demethanizer overhead stream 39 exits the top of demethanizer 17 at−146° F. [−99° C.] and is divided into cold residue gas stream 43 andrecycle stream 44. Recycle stream 44 is compressed to 492 psia [3,390kPa(a)] by compressor 21 before entering heat exchanger 22. Thecompressed recycle stream 44 a is cooled from −121° F. [−85° C.] to−140° F. [−96° C.] and substantially condensed by heat exchange withexpanded substantially condensed stream 36 b as described previously.The substantially condensed stream 44 b is then expanded through anappropriate expansion device, such as expansion valve 23, to thedemethanizer operating pressure, resulting in cooling of the totalstream to −150° F. [−101° C.]. The expanded stream 44 c is then suppliedto fractionation tower 17 as the top column feed. The vapor portion ofstream 44 c combines with the vapors rising from the top fractionationstage of the column to form demethanizer overhead stream 39.

The cold residue gas stream 43 passes countercurrently to the incomingfeed gas in heat exchanger 12 where it is heated to −26° F. [−32° C.](stream 43 a) and in heat exchanger 10 where it is heated to 98° F. [37°C.] (stream 43 b). The residue gas is then re-compressed in two stages.The first stage is compressor 15 driven by expansion machine 14. Thesecond stage is compressor 24 driven by a supplemental power sourcewhich compresses the residue gas (stream 43 d) to sales line pressure.After cooling to 120° F. [49° C.] in discharge cooler 25, the residuegas product (stream 43 e) flows to the sales gas pipeline at 1040 psia[7,171 kPa(a)], sufficient to meet line requirements (usually on theorder of the inlet pressure).

A summary of stream flow rates and energy consumption for the processillustrated in FIG. 1 is set forth in the following table:

TABLE I (FIG. 1) Stream Flow Summary - Lb. Moles/Hr [kg moles/Hr] StreamMethane Ethane Propane Butanes+ Total 31 24,193 1,650 687 234 27,451 3224,042 1,608 641 168 27,142 33 151 42 46 66 309 36 9,184 614 245 6410,368 37 14,858 994 396 104 16,774 39 28,419 82 0 0 29,216 44 4,263 120 0 4,382 43 24,156 70 0 0 24,834 42 37 1,580 687 234 2,617 Recoveries*Ethane 95.79% Propane 100.00% Butanes+ 100.00% Power Residue GasCompression 13,294 HP [21,855 kW] Recycle Compression 224 HP [368 kW]Total Compression 13,518 HP [22,223 kW] *(Based on un-rounded flowrates)

DESCRIPTION OF THE INVENTION

FIG. 2 illustrates a flow diagram of a process in accordance with thepresent invention. The feed gas composition and conditions considered inthe process presented in FIG. 2 are the same as those in FIG. 1.Accordingly, the FIG. 2 process can be compared with that of the FIG. 1process to illustrate the advantages of the present invention.

In the simulation of the FIG. 2 process, inlet gas enters the plant at120° F. [49° C.] and 1040 psia [7,171 kPa(a)] as stream 31 and is cooledin heat exchanger 10 by heat exchange with cool residue gas (stream 43a), liquid product at 74° F. [24° C.] (stream 42 a), demethanizerreboiler liquids at 54° F. [12° C.] (stream 41), and demethanizer sidereboiler liquids at −19° F. [−28° C.] (stream 40). The cooled stream 31a enters separator 11 at −24° F. [−31° C.] and 1025 psia [7,067 kPa(a)]where the vapor (stream 32) is separated from the condensed liquid(stream 33). The separator liquid (stream 33/38) is expanded to theoperating pressure (approximately 401 psia [2,766 kPa(a)]) offractionation tower 17 by expansion valve 16, cooling stream 38 a to−59° F. [−51° C.] before it is supplied to fractionation tower 17 at alower mid-column feed point (located below the feed point of stream 37 adescribed later in paragraph [0032]).

The vapor (stream 32) from separator 11 is divided into two streams, 34and 37. Stream 34, containing about 28% of the total vapor, passesthrough heat exchanger 12 in heat exchange relation with the coldresidue gas (stream 43) where it is cooled to substantial condensation.The resulting substantially condensed stream 36 a at −140° F. [−96° C.]is then flash expanded through expansion valve 13 to the operatingpressure of fractionation tower 17. During expansion a portion of thestream is vaporized, resulting in cooling of the total stream. In theprocess illustrated in FIG. 2, the expanded stream 36 b leavingexpansion valve 13 reaches a temperature of −144° F. [−98° C.] before itis supplied at an upper mid-column feed point, in absorbing section 17 aof fractionation tower 17.

The remaining 72% of the vapor from separator 11 (stream 37) enters awork expansion machine 14 in which mechanical energy is extracted fromthis portion of the high pressure feed. The machine 14 expands the vaporsubstantially isentropically to the tower operating pressure, with thework expansion cooling the expanded stream 37 a to a temperature ofapproximately −97° F. [−72° C.]. The partially condensed expanded stream37 a is thereafter supplied as feed to fractionation tower 17 at amid-column feed point (located below the feed point of stream 36 b).

The demethanizer in tower 17 is a conventional distillation columncontaining a plurality of vertically spaced trays, one or more packedbeds, or some combination of trays and packing. The demethanizer towerconsists of two sections: an upper absorbing (rectification) section 17a that contains the trays and/or packing to provide the necessarycontact between the vapor portion of the expanded streams 36 b and 37 arising upward and cold liquid falling downward to condense and absorbthe C₂ components, C₃ components, and heavier components from the vaporsrising upward; and a lower, stripping section 17 b that contains thetrays and/or packing to provide the necessary contact between theliquids falling downward and the vapors rising upward. The demethanizingsection 17 b also includes one or more reboilers (such as the reboilerand side reboiler described previously) which heat and vaporize aportion of the liquids flowing down the column to provide the strippingvapors which flow up the column to strip the liquid product, stream 42,of methane and lighter components. Stream 37 a enters demethanizer 17 atan intermediate feed position located in the lower region of absorbingsection 17 a of demethanizer 17. The liquid portion of the expandedstream 37 a commingles with liquids falling downward from absorbingsection 17 a and the combined liquid continues downward into strippingsection 17 b of demethanizer 17. The vapor portion of the expandedstream 37 a rises upward through absorbing section 17 a and is contactedwith cold liquid falling downward to condense and absorb the C₂components, C₃ components, and heavier components.

A portion of the distillation vapor (stream 45) is withdrawn from theupper region of absorbing section 17 a in fractionation column 17, abovethe feed position of expanded stream 36 b in the middle region ofabsorbing section 17 a. The distillation vapor stream 45 at −142° F.[−96° C.] is combined with a first portion (stream 44) of overhead vaporstream 39 at −144° F. [−98° C.] to form combined vapor stream 46 at−144° F. [−98° C.]. The combined vapor stream 46 is compressed to 686psia [4,728 kPa(a)] by reflux compressor 21, then cooled from −84° F.[−65° C.] to −140° F. [−96° C.] and substantially condensed (stream 46b) in heat exchanger 12 by heat exchange with cold residue gas stream43, the remaining second portion of demethanizer overhead stream 39exiting the top of demethanizer 17.

The substantially condensed stream 46 b is flash expanded to theoperating pressure of demethanizer 17 by expansion valve 23. A portionof the stream is vaporized, further cooling stream 46 c to −149° F.[−101° C.] before it is supplied as cold top column feed (reflux) todemethanizer 17. This cold liquid reflux absorbs and condenses the C₂components, C₃ components, and heavier components rising in the upperrectification region of absorbing section 17 a of demethanizer 17.

In stripping section 17 b of demethanizer 17, the feed streams arestripped of their methane and lighter components. The resulting liquidproduct (stream 42) exits the bottom of tower 17 at 69° F. [21° C.](based on a typical specification of a methane to ethane ratio of0.015:1 on a volume basis in the bottom product) and is pumped to heatexchanger 10 by pump 20 to be heated to 116° F. [47° C.] as it providescooling to the feed gas as described earlier. The cold residue gasstream 43 passes countercurrently to the incoming feed gas andcompressed combined vapor stream in heat exchanger 12 where it is heatedto −37° F. [−39° C.] (stream 43 a), and countercurrently to the incomingfeed gas in heat exchanger 10 where it is heated to 97° F. [36° C.](stream 43 b) as it provides cooling as previously described. Theresidue gas is then re-compressed in two stages, compressor 15 driven byexpansion machine 14 and compressor 24 driven by a supplemental powersource. After stream 43 d is cooled to 120° F. [49° C.] in dischargecooler 25, the residue gas product (stream 43 e) flows to the sales gaspipeline at 1040 psia [7,171 kPa(a)], sufficient to meet linerequirements (usually on the order of the inlet pressure).

A summary of stream flow rates and energy consumption for the processillustrated in FIG. 2 is set forth in the following table:

TABLE II (FIG. 2) Stream Flow Summary - Lb. Moles/Hr [kg moles/Hr]Stream Methane Ethane Propane Butanes+ Total 31 24,193 1,650 687 23427,451 32 23,983 1,593 626 157 27,042 33 210 57 61 77 409 34 6,607 439172 43 7,450 35 0 0 0 0 0 36 6,607 439 172 43 7,450 37 17,376 1,154 454114 19,592 38 210 57 61 77 409 39 27,081 78 0 0 27,845 44 2,925 8 0 03,007 45 194 1 0 0 200 46 3,119 9 0 0 3,207 43 24,156 70 0 0 24,838 4237 1,580 687 234 2,613 Recoveries* Ethane 95.77% Propane 99.99% Butanes+100.00% Power Residue Gas Compression 12,573 HP [20,670 kW] RefluxCompression 401 HP [659 kW] Total Compression 12,974 HP [21,329 kW]*(Based on un-rounded flow rates)

A comparison of Tables I and II shows that the present inventionmaintains essentially the same recoveries as the prior art. However,further comparison of Tables I and II shows that the product yields wereachieved using significantly less power than the prior art. In terms ofthe recovery efficiency (defined by the quantity of ethane recovered perunit of power), the present invention represents more than a 4%improvement over the prior art of the FIG. 1 process.

Like the prior art of the FIG. 1 process, the present invention uses theexpanded substantially condensed feed stream 36 b supplied to absorbingsection 17 a of demethanizer 17 to provide bulk recovery of the C₂components, C₃ components, and heavier hydrocarbon components containedin expanded feed 37 a and the vapors rising from stripping section 17 b,and the supplemental rectification provided by reflux stream 46 c toreduce the amount of C₂ components, C₃ components, and C₄+ componentscontained in the inlet feed gas that is lost to the residue gas.However, the present invention reduces the rectification required inabsorbing section 17 a over that of the prior art FIG. 1 process bycondensing reflux stream 46 c without warming any of the feeds (stream36 b and 37 a) to absorbing section 17 a. If the substantially condensedstream 36 b is warmed to provide condensing as is taught in the priorart FIG. 1 process, not only is there less cold liquid from stream 36 bavailable for rectification of the vapors rising in absorbing section 17a, there is much more vapor in the upper region of absorbing section 17a that must be rectified by the reflux stream. As can be seen bycomparing reflux stream 44 in Table I with reflux stream 46 in Table II,the net result is that more reflux is required by the prior art FIG. 1process to prevent the C₂ components from escaping to the residue gasstream than the present invention requires, reducing its recoveryefficiency compared to the present invention. The key improvement of thepresent invention over the prior art process is that only the coldresidue gas stream 43 is needed to provide the cooling in heat exchanger12, thereby condensing sufficient methane from compressed combined vaporstream 46 a for use as reflux while avoiding adding significantrectification load in absorbing section 17 a due to the excessivevaporization of stream 36 b that is inherent in the prior art FIG. 1process.

Other Embodiments

In accordance with this invention, it is generally advantageous todesign the absorbing (rectification) section of the demethanizer tocontain multiple theoretical separation stages. However, the benefits ofthe present invention can be achieved with as few as two theoreticalstages. For instance, all or a part of the expanded reflux stream(stream 46 c) leaving expansion valve 23 and all or a part of theexpanded substantially condensed stream 36 b from expansion valve 13 canbe combined (such as in the piping joining the expansion valves to thedemethanizer) and if thoroughly intermingled, the vapors and liquidswill mix together and separate in accordance with the relativevolatilities of the various components of the total combined streams.Such commingling of the two streams, combined with contacting at least aportion of expanded stream 37 a, shall be considered for the purposes ofthis invention as constituting an absorbing section.

FIGS. 3 through 6 display other embodiments of the present invention.FIGS. 2 through 4 depict fractionation towers constructed in a singlevessel. FIGS. 5 and 6 depict fractionation towers constructed in twovessels, absorber (rectifier) column 17 (a contacting and separatingdevice) and stripper (distillation) column 19. In such cases, theoverhead vapor stream 48 from stripper column 19 flows to the lowersection of absorber column 17 (via stream 49) to be contacted by refluxstream 46 c and expanded substantially condensed stream 36 b. Pump 18 isused to route the liquids (stream 47) from the bottom of absorber column17 to the top of stripper column 19 so that the two towers effectivelyfunction as one distillation system. The decision whether to constructthe fractionation tower as a single vessel (such as demethanizer 17 inFIGS. 2 through 4) or multiple vessels will depend on a number offactors such as plant size, the distance to fabrication facilities, etc.

Some circumstances may favor withdrawing the distillation vapor stream45 in FIGS. 3 and 4 from the lower region of absorbing section 17 aabove the feed point of expanded stream 37 a (stream 51), rather thanfrom the upper region of absorbing section 17 a above the feed point ofexpanded substantially condensed stream 36 b (stream 50). Likewise inFIGS. 5 and 6, the vapor distillation stream 45 may be withdrawn fromabsorber column 17 above the feed point of expanded substantiallycondensed stream 36 b (stream 50) or above the feed point of expandedstream 37 a (stream 51). In other cases, it may be advantageous towithdraw the distillation vapor stream 45 from the upper region ofstripping section 17 b in demethanizer 17 (stream 52) in FIGS. 3 and 4.Similarly in FIGS. 5 and 6, a portion (stream 52) of overhead vaporstream 48 from stripper column 19 may be combined with stream 44, withany remaining portion (stream 49) flowing to the lower section ofabsorber column 17.

As described earlier, the compressed combined vapor stream 46 a issubstantially condensed and the resulting condensate used to absorbvaluable C₂ components, C₃ components, and heavier components from thevapors rising through absorbing section 17 a of demethanizer 17 orthrough absorber column 17. However, the present invention is notlimited to this embodiment. It may be advantageous, for instance, totreat only a portion of these vapors in this manner, or to use only aportion of the condensate as an absorbent, in cases where other designconsiderations indicate portions of the vapors or the condensate shouldbypass absorbing section 17 a of demethanizer 17 or absorber column 17.Some circumstances may favor partial condensation, rather thansubstantial condensation, of compressed combined vapor stream 46 a inheat exchanger 12. Other circumstances may favor that distillation vaporstream 45 be a total vapor side draw from fractionation column 17 orabsorber column 17 rather than a partial vapor side draw. It should alsobe noted that, depending on the composition of the feed gas stream, itmay be advantageous to use external refrigeration to provide partialcooling of compressed combined vapor stream 46 a in heat exchanger 12.

Feed gas conditions, plant size, available equipment, or other factorsmay indicate that elimination of work expansion machine 14, orreplacement with an alternate expansion device (such as an expansionvalve), is feasible. Although individual stream expansion is depicted inparticular expansion devices, alternative expansion means may beemployed where appropriate. For example, conditions may warrant workexpansion of the substantially condensed portion of the feed stream(stream 36 a) or the substantially condensed reflux stream (stream 46 b)leaving heat exchanger 12.

Depending on the quantity of heavier hydrocarbons in the feed gas andthe feed gas pressure, the cooled feed stream 31 a leaving heatexchanger 10 in FIGS. 2 through 6 may not contain any liquid (because itis above its dewpoint, or because it is above its cricondenbar). In suchcases, separator 11 shown in FIGS. 2 through 6 is not required.

The high pressure liquid (stream 33 in FIGS. 2 through 6) need not beexpanded and fed to a mid-column feed point on the distillation column.Instead, all or a portion of it may be combined with the portion of theseparator vapor (stream 34) flowing to heat exchanger 12. (This is shownby the dashed stream 35 in FIGS. 2 through 6.) Any remaining portion ofthe liquid may be expanded through an appropriate expansion device, suchas an expansion valve or expansion machine, and fed to a mid-column feedpoint on the distillation column (stream 38 a in FIGS. 2 through 6).Stream 38 may also be used for inlet gas cooling or other heat exchangeservice before or after the expansion step prior to flowing to thedemethanizer.

In accordance with the present invention, the use of externalrefrigeration to supplement the cooling available to the inlet gas fromother process streams may be employed, particularly in the case of arich inlet gas. The use and distribution of separator liquids anddemethanizer side draw liquids for process heat exchange, and theparticular arrangement of heat exchangers for inlet gas cooling must beevaluated for each particular application, as well as the choice ofprocess streams for specific heat exchange services.

In accordance with the present invention, the splitting of the vaporfeed may be accomplished in several ways. In the processes of FIGS. 2,3, and 5, the splitting of vapor occurs following cooling and separationof any liquids which may have been formed. The high pressure gas may besplit, however, prior to any cooling of the inlet gas as shown in FIGS.4 and 6. In some embodiments, vapor splitting may be effected in aseparator.

It will also be recognized that the relative amount of feed found ineach branch of the split vapor feed will depend on several factors,including gas pressure, feed gas composition, the amount of heat whichcan economically be extracted from the feed, and the quantity ofhorsepower available. More feed to the top of the column may increaserecovery while decreasing power recovered from the expander therebyincreasing the recompression horsepower requirements. Increasing feedlower in the column reduces the horsepower consumption but may alsoreduce product recovery. The relative locations of the mid-column feedsmay vary depending on inlet composition or other factors such as desiredrecovery levels and amount of liquid formed during inlet gas cooling.Moreover, two or more of the feed streams, or portions thereof, may becombined depending on the relative temperatures and quantities ofindividual streams, and the combined stream then fed to a mid-columnfeed position.

The present invention provides improved recovery of C₂ components, C₃components, and heavier hydrocarbon components or of C₃ components andheavier hydrocarbon components per amount of utility consumptionrequired to operate the process. An improvement in utility consumptionrequired for operating the demethanizer or deethanizer process mayappear in the form of reduced power requirements for compression orre-compression, reduced power requirements for external refrigeration,reduced energy requirements for tower reboilers, or a combinationthereof.

While there have been described what are believed to be preferredembodiments of the invention, those skilled in the art will recognizethat other and further modifications may be made thereto, e.g. to adaptthe invention to various conditions, types of feed, or otherrequirements without departing from the spirit of the present inventionas defined by the following claims.

1. In a process for the separation of a gas stream containing methane,C₂ components, C₃ components, and heavier hydrocarbon components into avolatile residue gas fraction and a relatively less volatile fractioncontaining a major portion of said C₂ components, C₃ components, andheavier hydrocarbon components or said C₃ components and heavierhydrocarbon components, in which process (a) said gas stream is cooledunder pressure to provide a cooled stream; (b) said cooled stream isexpanded to a lower pressure whereby it is further cooled; and (c) saidfurther cooled stream is directed into a distillation column andfractionated at said lower pressure whereby the components of saidrelatively less volatile fraction are recovered; the improvement whereinfollowing cooling, said cooled stream is divided into first and secondstreams; and (1) said first stream is cooled to condense substantiallyall of it and is thereafter expanded to said lower pressure whereby itis further cooled; (2) said expanded cooled first stream is thereaftersupplied to said distillation column at an upper mid-column feedposition; (3) said second stream is expanded to said lower pressure andis supplied to said distillation column at a mid-column feed positionbelow said upper mid-column feed position; (4) an overhead vapor streamis withdrawn from an upper region of said distillation column anddivided into at least a first portion and a second portion; (5) adistillation vapor stream is withdrawn from a region of saiddistillation column above said upper mid-column feed position and iscombined with said first portion to form a combined vapor stream; (6)said combined vapor stream is compressed to higher pressure; (7) saidcompressed combined vapor stream is directed into heat exchange relationwith said second portion, whereby said second portion is heated and saidcompressed combined vapor stream is cooled sufficiently to condense atleast a part of it and thereby form a condensed stream, and thereafterdischarging at least a portion of said heated second portion as saidvolatile residue gas fraction; (8) at least a portion of said condensedstream is expanded to said lower pressure and is thereafter supplied tosaid distillation column at a top feed position; and (9) the quantitiesand temperatures of said feed streams to said distillation column areeffective to maintain the overhead temperature of said distillationcolumn at a temperature whereby the major portions of the components insaid relatively less volatile fraction are recovered.
 2. In a processfor the separation of a gas stream containing methane, C₂ components, C₃components, and heavier hydrocarbon components into a volatile residuegas fraction and a relatively less volatile fraction containing a majorportion of said C₂ components, C₃ components, and heavier hydrocarboncomponents or said C₃ components and heavier hydrocarbon components, inwhich process (a) said gas stream is cooled under pressure to provide acooled stream; (b) said cooled stream is expanded to a lower pressurewhereby it is further cooled; and (c) said further cooled stream isdirected into a distillation column and fractionated at said lowerpressure whereby the components of said relatively less volatilefraction are recovered; the improvement wherein prior to cooling, saidgas stream is divided into first and second streams; and (1) said firststream is cooled to condense substantially all of it and is thereafterexpanded to said lower pressure whereby it is further cooled; (2) saidexpanded cooled first stream is thereafter supplied to said distillationcolumn at an upper mid-column feed position; (3) said second stream iscooled and thereafter expanded to said lower pressure and supplied tosaid distillation column at a mid-column feed position below said uppermid-column feed position; (4) an overhead vapor stream is withdrawn froman upper region of said distillation column and divided into at least afirst portion and a second portion; (5) a distillation vapor stream iswithdrawn from a region of said distillation column above said uppermid-column feed position and is combined with said first portion to forma combined vapor stream; (6) said combined vapor stream is compressed tohigher pressure; (7) said compressed combined vapor stream is directedinto heat exchange relation with said second portion, whereby saidsecond portion is heated and said compressed combined vapor stream iscooled sufficiently to condense at least a part of it and thereby form acondensed stream, and thereafter discharging at least a portion of saidheated second portion as said volatile residue gas fraction; (8) atleast a portion of said condensed stream is expanded to said lowerpressure and is thereafter supplied to said distillation column at a topfeed position; and (9) the quantities and temperatures of said feedstreams to said distillation column are effective to maintain theoverhead temperature of said distillation column at a temperaturewhereby the major portions of the components in said relatively lessvolatile fraction are recovered.
 3. In a process for the separation of agas stream containing methane, C₂ components, C₃ components, and heavierhydrocarbon components into a volatile residue gas fraction and arelatively less volatile fraction containing a major portion of said C₂components, C₃ components, and heavier hydrocarbon components or said C₃components and heavier hydrocarbon components, in which process (a) saidgas stream is cooled under pressure to provide a cooled stream; (b) saidcooled stream is expanded to a lower pressure whereby it is furthercooled; and (c) said further cooled stream is directed into adistillation column and fractionated at said lower pressure whereby thecomponents of said relatively less volatile fraction are recovered; theimprovement wherein said gas stream is cooled sufficiently to partiallycondense it; and (1) said partially condensed gas stream is separatedthereby to provide a vapor stream and at least one liquid stream; (2)said vapor stream is thereafter divided into first and second streams;(3) said first stream is cooled to condense substantially all of it andis thereafter expanded to said lower pressure whereby it is furthercooled; (4) said expanded cooled first stream is thereafter supplied tosaid distillation column at an upper mid-column feed position; (5) saidsecond stream is expanded to said lower pressure and is supplied to saiddistillation column at a mid-column feed position below said uppermid-column feed position; (6) at least a portion of said at least oneliquid stream is expanded to said lower pressure and is supplied to saiddistillation column at a lower mid-column feed position below saidmid-column feed position; (7) an overhead vapor stream is withdrawn froman upper region of said distillation column and divided into at least afirst portion and a second portion; (8) a distillation vapor stream iswithdrawn from a region of said distillation column above said uppermid-column feed position and is combined with said first portion to forma combined vapor stream; (9) said combined vapor stream is compressed tohigher pressure; (10) said compressed combined vapor stream is directedinto heat exchange relation with said second portion, whereby saidsecond portion is heated and said compressed combined vapor stream iscooled sufficiently to condense at least a part of it and thereby form acondensed stream, and thereafter discharging at least a portion of saidheated second portion as said volatile residue gas fraction; (11) atleast a portion of said condensed stream is expanded to said lowerpressure and is thereafter supplied to said distillation column at a topfeed position; and (12) the quantities and temperatures of said feedstreams to said distillation column are effective to maintain theoverhead temperature of said distillation column at a temperaturewhereby the major portions of the components in said relatively lessvolatile fraction are recovered.
 4. In a process for the separation of agas stream containing methane, C₂ components, C₃ components, and heavierhydrocarbon components into a volatile residue gas fraction and arelatively less volatile fraction containing a major portion of said C₂components, C₃ components, and heavier hydrocarbon components or said C₃components and heavier hydrocarbon components, in which process (a) saidgas stream is cooled under pressure to provide a cooled stream; (b) saidcooled stream is expanded to a lower pressure whereby it is furthercooled; and (c) said further cooled stream is directed into adistillation column and fractionated at said lower pressure whereby thecomponents of said relatively less volatile fraction are recovered; theimprovement wherein prior to cooling, said gas stream is divided intofirst and second streams; and (1) said first stream is cooled tocondense substantially all of it and is thereafter expanded to saidlower pressure whereby it is further cooled; (2) said expanded cooledfirst stream is thereafter supplied to said distillation column at anupper mid-column feed position; (3) said second stream is cooled underpressure sufficiently to partially condense it; (4) said partiallycondensed second stream is separated thereby to provide a vapor streamand at least one liquid stream; (5) said vapor stream is expanded tosaid lower pressure and is supplied to said distillation column at amid-column feed position below said upper mid-column feed position; (6)at least a portion of said at least one liquid stream is expanded tosaid lower pressure and is supplied to said distillation column at alower mid-column feed position below said mid-column feed position; (7)an overhead vapor stream is withdrawn from an upper region of saiddistillation column and divided into at least a first portion and asecond portion; (8) a distillation vapor stream is withdrawn from aregion of said distillation column above said upper mid-column feedposition and is combined with said first portion to form a combinedvapor stream; (9) said combined vapor stream is compressed to higherpressure; (10) said compressed combined vapor stream is directed intoheat exchange relation with said second portion, whereby said secondportion is heated and said compressed combined vapor stream is cooledsufficiently to condense at least a part of it and thereby form acondensed stream, and thereafter discharging at least a portion of saidheated second portion as said volatile residue gas fraction; (11) atleast a portion of said condensed stream is expanded to said lowerpressure and is thereafter supplied to said distillation column at a topfeed position; and (12) the quantities and temperatures of said feedstreams to said distillation column are effective to maintain theoverhead temperature of said distillation column at a temperaturewhereby the major portions of the components in said relatively lessvolatile fraction are recovered.
 5. In a process for the separation of agas stream containing methane, C₂ components, C₃ components, and heavierhydrocarbon components into a volatile residue gas fraction and arelatively less volatile fraction containing a major portion of said C₂components, C₃ components, and heavier hydrocarbon components or said C₃components and heavier hydrocarbon components, in which process (a) saidgas stream is cooled under pressure to provide a cooled stream; (b) saidcooled stream is expanded to a lower pressure whereby it is furthercooled; and (c) said further cooled stream is directed into adistillation column and fractionated at said lower pressure whereby thecomponents of said relatively less volatile fraction are recovered; theimprovement wherein said gas stream is cooled sufficiently to partiallycondense it; and (1) said partially condensed gas stream is separatedthereby to provide a vapor stream and at least one liquid stream; (2)said vapor stream is thereafter divided into first and second streams;(3) said first stream is combined with at least a portion of said atleast one liquid stream to form a combined stream, whereupon saidcombined stream is cooled to condense substantially all of it and isthereafter expanded to said lower pressure whereby it is further cooled;(4) said expanded cooled combined stream is thereafter supplied to saiddistillation column at an upper mid-column feed position; (5) saidsecond stream is expanded to said lower pressure and is supplied to saiddistillation column at a mid-column feed position below said uppermid-column feed position; (6) any remaining portion of said at least oneliquid stream is expanded to said lower pressure and is supplied to saiddistillation column at a lower mid-column feed position below saidmid-column feed position; (7) an overhead vapor stream is withdrawn froman upper region of said distillation column and divided into at least afirst portion and a second portion; (8) a distillation vapor stream iswithdrawn from a region of said distillation column above said uppermid-column feed position and is combined with said first portion to forma combined vapor stream; (9) said combined vapor stream is compressed tohigher pressure; (10) said compressed combined vapor stream is directedinto heat exchange relation with said second portion, whereby saidsecond portion is heated and said compressed combined vapor stream iscooled sufficiently to condense at least a part of it and thereby form acondensed stream, and thereafter discharging at least a portion of saidheated second portion as said volatile residue gas fraction; (11) atleast a portion of said condensed stream is expanded to said lowerpressure and is thereafter supplied to said distillation column at a topfeed position; and (12) the quantities and temperatures of said feedstreams to said distillation column are effective to maintain theoverhead temperature of said distillation column at a temperaturewhereby the major portions of the components in said relatively lessvolatile fraction are recovered.
 6. In a process for the separation of agas stream containing methane, C₂ components, C₃ components, and heavierhydrocarbon components into a volatile residue gas fraction and arelatively less volatile fraction containing a major portion of said C₂components, C₃ components, and heavier hydrocarbon components or said C₃components and heavier hydrocarbon components, in which process (a) saidgas stream is cooled under pressure to provide a cooled stream; (b) saidcooled stream is expanded to a lower pressure whereby it is furthercooled; and (c) said further cooled stream is directed into adistillation column and fractionated at said lower pressure whereby thecomponents of said relatively less volatile fraction are recovered; theimprovement wherein following cooling, said cooled stream is dividedinto first and second streams; and (1) said first stream is cooled tocondense substantially all of it and is thereafter expanded to saidlower pressure whereby it is further cooled; (2) said expanded cooledfirst stream is thereafter supplied at a mid-column feed position to acontacting and separating device that produces a first overhead vaporstream and a bottom liquid stream, whereupon said bottom liquid streamis supplied to said distillation column; (3) said second stream isexpanded to said lower pressure and is supplied to said contacting andseparating device at a first lower column feed position below saidmid-column feed position; (4) a second overhead vapor stream iswithdrawn from an upper region of said distillation column and issupplied to said contacting and separating device at a second lowercolumn feed position below said mid-column feed position; (5) said firstoverhead vapor stream is divided into at least a first portion and asecond portion; (6) a distillation vapor stream is withdrawn from aregion of said contacting and separating device above said mid-columnfeed position and is combined with said first portion to form a combinedvapor stream; (7) said combined vapor stream is compressed to higherpressure; (8) said compressed combined vapor stream is directed intoheat exchange relation with said second portion, whereby said secondportion is heated and said compressed combined vapor stream is cooledsufficiently to condense at least a part of it and thereby form acondensed stream, and thereafter discharging at least a portion of saidheated second portion as said volatile residue gas fraction; (9) atleast a portion of said condensed stream is expanded to said lowerpressure and is thereafter supplied to said contacting and separatingdevice at a top feed position; and (10) the quantities and temperaturesof said feed streams to said contacting and separating device areeffective to maintain the overhead temperature of said contacting andseparating device at a temperature whereby the major portions of thecomponents in said relatively less volatile fraction are recovered. 7.In a process for the separation of a gas stream containing methane, C₂components, C₃ components, and heavier hydrocarbon components into avolatile residue gas fraction and a relatively less volatile fractioncontaining a major portion of said C₂ components, C₃ components, andheavier hydrocarbon components or said C₃ components and heavierhydrocarbon components, in which process (a) said gas stream is cooledunder pressure to provide a cooled stream; (b) said cooled stream isexpanded to a lower pressure whereby it is further cooled; and (c) saidfurther cooled stream is directed into a distillation column andfractionated at said lower pressure whereby the components of saidrelatively less volatile fraction are recovered; the improvement whereinprior to cooling, said gas stream is divided into first and secondstreams; and (1) said first stream is cooled to condense substantiallyall of it and is thereafter expanded to said lower pressure whereby itis further cooled; (2) said expanded cooled first stream is thereaftersupplied at a mid-column feed position to a contacting and separatingdevice that produces a first overhead vapor stream and a bottom liquidstream, whereupon said bottom liquid stream is supplied to saiddistillation column; (3) said second stream is cooled and thereafterexpanded to said lower pressure and supplied to said contacting andseparating device at a first lower column feed position below saidmid-column feed position; (4) a second overhead vapor stream iswithdrawn from an upper region of said distillation column and issupplied to said contacting and separating device at a second lowercolumn feed position below said mid-column feed position; (5) said firstoverhead vapor stream is divided into at least a first portion and asecond portion; (6) a distillation vapor stream is withdrawn from aregion of said contacting and separating device above said mid-columnfeed position and is combined with said first portion to form a combinedvapor stream; (7) said combined vapor stream is compressed to higherpressure; (8) said compressed combined vapor stream is directed intoheat exchange relation with said second portion, whereby said secondportion is heated and said compressed combined vapor stream is cooledsufficiently to condense at least a part of it and thereby form acondensed stream, and thereafter discharging at least a portion of saidheated second portion as said volatile residue gas fraction; (9) atleast a portion of said condensed stream is expanded to said lowerpressure and is thereafter supplied to said contacting and separatingdevice at a top feed position; and (10) the quantities and temperaturesof said feed streams to said contacting and separating device areeffective to maintain the overhead temperature of said contacting andseparating device at a temperature whereby the major portions of thecomponents in said relatively less volatile fraction are recovered. 8.In a process for the separation of a gas stream containing methane, C₂components, C₃ components, and heavier hydrocarbon components into avolatile residue gas fraction and a relatively less volatile fractioncontaining a major portion of said C₂ components, C₃ components, andheavier hydrocarbon components or said C₃ components and heavierhydrocarbon components, in which process (a) said gas stream is cooledunder pressure to provide a cooled stream; (b) said cooled stream isexpanded to a lower pressure whereby it is further cooled; and (c) saidfurther cooled stream is directed into a distillation column andfractionated at said lower pressure whereby the components of saidrelatively less volatile fraction are recovered; the improvement whereinsaid gas stream is cooled sufficiently to partially condense it; and (1)said partially condensed gas stream is separated thereby to provide avapor stream and at least one liquid stream; (2) said vapor stream isthereafter divided into first and second streams; (3) said first streamis cooled to condense substantially all of it and is thereafter expandedto said lower pressure whereby it is further cooled; (4) said expandedcooled first stream is thereafter supplied at a mid-column feed positionto a contacting and separating device that produces a first overheadvapor stream and a bottom liquid stream, whereupon said bottom liquidstream is supplied to said distillation column; (5) said second streamis expanded to said lower pressure and is supplied to said contactingand separating device at a first lower column feed position below saidmid-column feed position; (6) at least a portion of said at least oneliquid stream is expanded to said lower pressure and is supplied to saiddistillation column at a mid-column feed position; (7) a second overheadvapor stream is withdrawn from an upper region of said distillationcolumn and is supplied to said contacting and separating device at asecond lower column feed position below said mid-column feed position;(8) said first overhead vapor stream is divided into at least a firstportion and a second portion; (9) a distillation vapor stream iswithdrawn from a region of said contacting and separating device abovesaid mid-column feed position and is combined with said first portion toform a combined vapor stream; (10) said combined vapor stream iscompressed to higher pressure; (11) said compressed combined vaporstream is directed into heat exchange relation with said second portion,whereby said second portion is heated and said compressed combined vaporstream is cooled sufficiently to condense at least a part of it andthereby form a condensed stream, and thereafter discharging at least aportion of said heated second portion as said volatile residue gasfraction; (12) at least a portion of said condensed stream is expandedto said lower pressure and is thereafter supplied to said contacting andseparating device at a top feed position; and (13) the quantities andtemperatures of said feed streams to said contacting and separatingdevice are effective to maintain the overhead temperature of saidcontacting and separating device at a temperature whereby the majorportions of the components in said relatively less volatile fraction arerecovered.
 9. In a process for the separation of a gas stream containingmethane, C₂ components, C₃ components, and heavier hydrocarboncomponents into a volatile residue gas fraction and a relatively lessvolatile fraction containing a major portion of said C₂ components, C₃components, and heavier hydrocarbon components or said C₃ components andheavier hydrocarbon components, in which process (a) said gas stream iscooled under pressure to provide a cooled stream; (b) said cooled streamis expanded to a lower pressure whereby it is further cooled; and (c)said further cooled stream is directed into a distillation column andfractionated at said lower pressure whereby the components of saidrelatively less volatile fraction are recovered; the improvement whereinprior to cooling, said gas stream is divided into first and secondstreams; and (1) said first stream is cooled to condense substantiallyall of it and is thereafter expanded to said lower pressure whereby itis further cooled; (2) said expanded cooled first stream is thereaftersupplied at a mid-column feed position to a contacting and separatingdevice that produces an overhead vapor stream and a bottom liquidstream, whereupon said bottom liquid stream is supplied to saiddistillation column; (3) said second stream is cooled under pressuresufficiently to partially condense it; (4) said partially condensedsecond stream is separated thereby to provide a vapor stream and atleast one liquid stream; (5) said vapor stream is expanded to said lowerpressure and is supplied to said contacting and separating device at afirst lower column feed position below said mid-column feed position;(6) at least a portion of said at least one liquid stream is expanded tosaid lower pressure and is supplied to said distillation column at amid-column feed position; (7) a second overhead vapor stream iswithdrawn from an upper region of said distillation column and issupplied to said contacting and separating device at a second lowercolumn feed position below said mid-column feed position; (8) said firstoverhead vapor stream is divided into at least a first portion and asecond portion; (9) a distillation vapor stream is withdrawn from aregion of said contacting and separating device above said mid-columnfeed position and is combined with said first portion to form a combinedvapor stream; (10) said combined vapor stream is compressed to higherpressure; (11) said compressed combined vapor stream is directed intoheat exchange relation with said second portion, whereby said secondportion is heated and said compressed combined vapor stream is cooledsufficiently to condense at least a part of it and thereby form acondensed stream, and thereafter discharging at least a portion of saidheated second portion as said volatile residue gas fraction; (12) atleast a portion of said condensed stream is expanded to said lowerpressure and is thereafter supplied to said contacting and separatingdevice at a top feed position; and (13) the quantities and temperaturesof said feed streams to said contacting and separating device areeffective to maintain the overhead temperature of said contacting andseparating device at a temperature whereby the major portions of thecomponents in said relatively less volatile fraction are recovered. 10.In a process for the separation of a gas stream containing methane, C₂components, C₃ components, and heavier hydrocarbon components into avolatile residue gas fraction and a relatively less volatile fractioncontaining a major portion of said C₂ components, C₃ components, andheavier hydrocarbon components or said C₃ components and heavierhydrocarbon components, in which process (a) said gas stream is cooledunder pressure to provide a cooled stream; (b) said cooled stream isexpanded to a lower pressure whereby it is further cooled; and (c) saidfurther cooled stream is directed into a distillation column andfractionated at said lower pressure whereby the components of saidrelatively less volatile fraction are recovered; the improvement whereinsaid gas stream is cooled sufficiently to partially condense it; and (1)said partially condensed gas stream is separated thereby to provide avapor stream and at least one liquid stream; (2) said vapor stream isthereafter divided into first and second streams; (3) said first streamis combined with at least a portion of said at least one liquid streamto form a combined stream, whereupon said combined stream is cooled tocondense substantially all of it and is thereafter expanded to saidlower pressure whereby it is further cooled; (4) said expanded cooledcombined stream is thereafter supplied at a mid-column feed position toa contacting and separating device that produces a first overhead vaporstream and a bottom liquid stream, whereupon said bottom liquid streamis supplied to said distillation column; (5) said second stream isexpanded to said lower pressure and is supplied to said contacting andseparating device at a first lower column feed position below saidmid-column feed position; (6) any remaining portion of said at least oneliquid stream is expanded to said lower pressure and is supplied to saiddistillation column at a mid-column feed position; (7) a second overheadvapor stream is withdrawn from an upper region of said distillationcolumn and is supplied to said contacting and separating device at asecond lower column feed position below said mid-column feed position;(8) said first overhead vapor stream is divided into at least a firstportion and a second portion; (9) a distillation vapor stream iswithdrawn from a region of said contacting and separating device abovesaid mid-column feed position and is combined with said first portion toform a combined vapor stream; (10) said combined vapor stream iscompressed to higher pressure; (11) said compressed combined vaporstream is directed into heat exchange relation with said second portion,whereby said second portion is heated and said compressed combined vaporstream is cooled sufficiently to condense at least a part of it andthereby form a condensed stream, and thereafter discharging at least aportion of said heated second portion as said volatile residue gasfraction; (12) at least a portion of said condensed stream is expandedto said lower pressure and is thereafter supplied to said contacting andseparating device at a top feed position; and (13) the quantities andtemperatures of said feed streams to said contacting and separatingdevice are effective to maintain the overhead temperature of saidcontacting and separating device at a temperature whereby the majorportions of the components in said relatively less volatile fraction arerecovered.
 11. The improvement according to claim 1, 2, 3, 4, or 5wherein said distillation vapor stream is withdrawn from a region ofsaid distillation column below said upper mid-column feed position andabove said mid-column feed position.
 12. The improvement according toclaim 1, 2, 3, 4, or 5 wherein said distillation vapor stream iswithdrawn from a region of said distillation column below saidmid-column feed position.
 13. The improvement according to claim 6, 7,8, 9, or 10 wherein said distillation vapor stream is withdrawn from aregion of said contacting and separating device below said mid-columnfeed position and above said first and second lower column feedpositions.
 14. The improvement according to claim 6, 7, 8, 9, or 10wherein said second overhead vapor stream is divided into saiddistillation vapor stream and a second distillation vapor stream,whereupon said second distillation vapor stream is supplied to saidcontacting and separating device at said second lower column feedposition.
 15. In an apparatus for the separation of a gas streamcontaining methane, C₂ components, C₃ components, and heavierhydrocarbon components into a volatile residue gas fraction and arelatively less volatile fraction containing a major portion of said C₂components, C₃ components, and heavier hydrocarbon components or said C₃components and heavier hydrocarbon components, in said apparatus therebeing (a) a first cooling means to cool said gas stream under pressureconnected to provide a cooled stream under pressure; (b) a firstexpansion means connected to receive at least a portion of said cooledstream under pressure and expand it to a lower pressure, whereby saidstream is further cooled; and (c) a distillation column connected toreceive said further cooled stream, said distillation column beingadapted to separate said further cooled stream into an overhead vaporstream and said relatively less volatile fraction; the improvementwherein said apparatus includes (1) first dividing means connected tosaid first cooling means to receive said cooled stream and divide itinto first and second streams; (2) second cooling means connected tosaid first dividing means to receive said first stream and cool itsufficiently to substantially condense it; (3) second expansion meansconnected to said second cooling means to receive said substantiallycondensed first stream and expand it to said lower pressure, said secondexpansion means being further connected to said distillation column tosupply said expanded cooled first stream to said distillation column atan upper mid-column feed position; (4) said first expansion means beingconnected to said first dividing means to receive said second stream andexpand it to said lower pressure, said first expansion means beingfurther connected to said distillation column to supply said expandedsecond stream to said distillation column at a mid-column feed positionbelow said upper mid-column feed position; (5) second dividing meansconnected to said distillation column to receive said overhead vaporstream separated therein and divide it into at least a first portion anda second portion; (6) heat exchange means connected to said seconddividing means to receive at least a portion of said second portion andheat it, thereafter discharging at least a portion of said heated secondportion as said volatile residue gas fraction; (7) vapor withdrawingmeans connected to said distillation column to receive a distillationvapor stream from a region of said distillation column above said uppermid-column feed position; (8) combining means connected to said seconddividing means and said vapor withdrawing means to receive said firstportion and said distillation vapor stream and form a combined vaporstream; (9) compressing means connected to said combining means toreceive said combined vapor stream and compress it to higher pressure;(10) said heat exchange means being further connected to saidcompressing means to receive said compressed combined vapor stream andcool it sufficiently to condense at least a part of it, thereby forminga condensed stream while supplying at least a portion of the heating ofstep (6); (11) third expansion means connected to said heat exchangemeans to receive said condensed stream and expand it to said lowerpressure, said third expansion means being further connected to saiddistillation column to supply at least a portion of said expandedcondensed stream to said distillation column at a top feed position; and(12) control means adapted to regulate the quantities and temperaturesof said feed streams to said distillation column to maintain theoverhead temperature of said distillation column at a temperaturewhereby the major portions of the components in said relatively lessvolatile fraction are recovered.
 16. In an apparatus for the separationof a gas stream containing methane, C₂ components, C₃ components, andheavier hydrocarbon components into a volatile residue gas fraction anda relatively less volatile fraction containing a major portion of saidC₂ components, C₃ components, and heavier hydrocarbon components or saidC₃ components and heavier hydrocarbon components, in said apparatusthere being (a) a first cooling means to cool said gas stream underpressure connected to provide a cooled stream under pressure; (b) afirst expansion means connected to receive at least a portion of saidcooled stream under pressure and expand it to a lower pressure, wherebysaid stream is further cooled; and (c) a distillation column connectedto receive said further cooled stream, said distillation column beingadapted to separate said further cooled stream into an overhead vaporstream and said relatively less volatile fraction; the improvementwherein said apparatus includes (1) first dividing means prior to saidfirst cooling means to divide said gas stream into first and secondstreams; (2) second cooling means connected to said first dividing meansto receive said first stream and cool it sufficiently to substantiallycondense it; (3) second expansion means connected to said second coolingmeans to receive said substantially condensed first stream and expand itto said lower pressure, said second expansion means being furtherconnected to said distillation column to supply said expanded cooledfirst stream to said distillation column at an upper mid-column feedposition; (4) said first cooling means being connected to said firstdividing means to receive said second stream and cool it; (5) said firstexpansion means being connected to said first cooling means to receivesaid cooled second stream and expand it to said lower pressure, saidfirst expansion means being further connected to said distillationcolumn to supply said expanded cooled second stream to said distillationcolumn at a mid-column feed position below said upper mid-column feedposition; (6) second dividing means connected to said distillationcolumn to receive said overhead vapor stream separated therein anddivide it into at least a first portion and a second portion; (7) heatexchange means connected to said second dividing means to receive atleast a portion of said second portion and heat it, thereafterdischarging at least a portion of said heated second portion as saidvolatile residue gas fraction; (8) vapor withdrawing means connected tosaid distillation column to receive a distillation vapor stream from aregion of said distillation column above said upper mid-column feedposition; (9) combining means connected to said second dividing meansand said vapor withdrawing means to receive said first portion and saiddistillation vapor stream and form a combined vapor stream; (10)compressing means connected to said combining means to receive saidcombined vapor stream and compress it to higher pressure; (11) said heatexchange means being further connected to said compressing means toreceive said compressed combined vapor stream and cool it sufficientlyto condense at least a part of it, thereby forming a condensed streamwhile supplying at least a portion of the heating of step (7); (12)third expansion means connected to said heat exchange means to receivesaid condensed stream and expand it to said lower pressure, said thirdexpansion means being further connected to said distillation column tosupply at least a portion of said expanded condensed stream to saiddistillation column at a top feed position; and (13) control meansadapted to regulate the quantities and temperatures of said feed streamsto said distillation column to maintain the overhead temperature of saiddistillation column at a temperature whereby the major portions of thecomponents in said relatively less volatile fraction are recovered. 17.In an apparatus for the separation of a gas stream containing methane,C₂ components, C₃ components, and heavier hydrocarbon components into avolatile residue gas fraction and a relatively less volatile fractioncontaining a major portion of said C₂ components, C₃ components, andheavier hydrocarbon components or said C₃ components and heavierhydrocarbon components, in said apparatus there being (a) a firstcooling means to cool said gas stream under pressure connected toprovide a cooled stream under pressure; (b) a first expansion meansconnected to receive at least a portion of said cooled stream underpressure and expand it to a lower pressure, whereby said stream isfurther cooled; and (c) a distillation column connected to receive saidfurther cooled stream, said distillation column being adapted toseparate said further cooled stream into an overhead vapor stream andsaid relatively less volatile fraction; the improvement wherein saidapparatus includes (1) said first cooling means being adapted to coolsaid gas stream under pressure sufficiently to partially condense it;(2) separating means connected to said first cooling means to receivesaid partially condensed gas stream and separate it into a vapor streamand at least one liquid stream; (3) first dividing means connected tosaid separating means to receive said vapor stream and divide it intofirst and second streams; (4) second cooling means connected to saidfirst dividing means to receive said first stream and cool itsufficiently to substantially condense it; (5) second expansion meansconnected to said second cooling means to receive said substantiallycondensed first stream and expand it to said lower pressure, said secondexpansion means being further connected to said distillation column tosupply said expanded cooled first stream to said distillation column atan upper mid-column feed position; (6) said first expansion means beingconnected to said first dividing means to receive said second stream andexpand it to said lower pressure, said first expansion means beingfurther connected to said distillation column to supply said expandedsecond stream to said distillation column at a mid-column feed positionbelow said upper mid-column feed position; (7) third expansion meansconnected to said separating means to receive at least a portion of saidat least one liquid stream and expand it to said lower pressure, saidthird expansion means being further connected to said distillationcolumn to supply said expanded liquid stream to said distillation columnat a lower mid-column feed position below said mid-column feed position;(8) second dividing means connected to said distillation column toreceive said overhead vapor stream separated therein and divide it intoat least a first portion and a second portion; (9) heat exchange meansconnected to said second dividing means to receive at least a portion ofsaid second portion and heat it, thereafter discharging at least aportion of said heated second portion as said volatile residue gasfraction; (10) vapor withdrawing means connected to said distillationcolumn to receive a distillation vapor stream from a region of saiddistillation column above said upper mid-column feed position; (11)combining means connected to said second dividing means and said vaporwithdrawing means to receive said first portion and said distillationvapor stream and form a combined vapor stream; (12) compressing meansconnected to said combining means to receive said combined vapor streamand compress it to higher pressure; (13) said heat exchange means beingfurther connected to said compressing means to receive said compressedcombined vapor stream and cool it sufficiently to condense at least apart of it, thereby forming a condensed stream while supplying at leasta portion of the heating of step (9); (14) fourth expansion meansconnected to said heat exchange means to receive said condensed streamand expand it to said lower pressure, said fourth expansion means beingfurther connected to said distillation column to supply at least aportion of said expanded condensed stream to said distillation column ata top feed position; and (15) control means adapted to regulate thequantities and temperatures of said feed streams to said distillationcolumn to maintain the overhead temperature of said distillation columnat a temperature whereby the major portions of the components in saidrelatively less volatile fraction are recovered.
 18. In an apparatus forthe separation of a gas stream containing methane, C₂ components, C₃components, and heavier hydrocarbon components into a volatile residuegas fraction and a relatively less volatile fraction containing a majorportion of said C₂ components, C₃ components, and heavier hydrocarboncomponents or said C₃ components and heavier hydrocarbon components, insaid apparatus there being (a) a first cooling means to cool said gasstream under pressure connected to provide a cooled stream underpressure; (b) a first expansion means connected to receive at least aportion of said cooled stream under pressure and expand it to a lowerpressure, whereby said stream is further cooled; and (c) a distillationcolumn connected to receive said further cooled stream, saiddistillation column being adapted to separate said further cooled streaminto an overhead vapor stream and said relatively less volatilefraction; the improvement wherein said apparatus includes (1) firstdividing means prior to said first cooling means to divide said gasstream into first and second streams; (2) second cooling means connectedto said first dividing means to receive said first stream and cool itsufficiently to substantially condense it; (3) second expansion meansconnected to said second cooling means to receive said substantiallycondensed first stream and expand it to said lower pressure, said secondexpansion means being further connected to said distillation column tosupply said expanded cooled first stream to said distillation column atan upper mid-column feed position; (4) said first cooling means beingconnected to said first dividing means to receive said second stream,said first cooling means being adapted to cool said second stream underpressure sufficiently to partially condense it; (5) separating meansconnected to said first cooling means to receive said partiallycondensed second stream and separate it into a vapor stream and at leastone liquid stream; (6) said first expansion means being connected tosaid separating means to receive said vapor stream and expand it to saidlower pressure, said first expansion means being further connected tosaid distillation column to supply said expanded vapor stream to saiddistillation column at a mid-column feed position below said uppermid-column feed position; (7) third expansion means connected to saidseparating means to receive at least a portion of said at least oneliquid stream and expand it to said lower pressure, said third expansionmeans being further connected to said distillation column to supply saidexpanded liquid stream to said distillation column at a lower mid-columnfeed position below said mid-column feed position; (8) second dividingmeans connected to said distillation column to receive said overheadvapor stream separated therein and divide it into at least a firstportion and a second portion; (9) heat exchange means connected to saidsecond dividing means to receive at least a portion of said secondportion and heat it, thereafter discharging at least a portion of saidheated second portion as said volatile residue gas fraction; (10) vaporwithdrawing means connected to said distillation column to receive adistillation vapor stream from a region of said distillation columnabove said upper mid-column feed position; (11) combining meansconnected to said second dividing means and said vapor withdrawing meansto receive said first portion and said distillation vapor stream andform a combined vapor stream; (12) compressing means connected to saidcombining means to receive said combined vapor stream and compress it tohigher pressure; (13) said heat exchange means being further connectedto said compressing means to receive said compressed combined vaporstream and cool it sufficiently to condense at least a part of it,thereby forming a condensed stream while supplying at least a portion ofthe heating of step (9); (14) fourth expansion means connected to saidheat exchange means to receive said condensed stream and expand it tosaid lower pressure, said fourth expansion means being further connectedto said distillation column to supply at least a portion of saidexpanded condensed stream to said distillation column at a top feedposition; and (15) control means adapted to regulate the quantities andtemperatures of said feed streams to said distillation column tomaintain the overhead temperature of said distillation column at atemperature whereby the major portions of the components in saidrelatively less volatile fraction are recovered.
 19. In an apparatus forthe separation of a gas stream containing methane, C₂ components, C₃components, and heavier hydrocarbon components into a volatile residuegas fraction and a relatively less volatile fraction containing a majorportion of said C₂ components, C₃ components, and heavier hydrocarboncomponents or said C₃ components and heavier hydrocarbon components, insaid apparatus there being (a) a first cooling means to cool said gasstream under pressure connected to provide a cooled stream underpressure; (b) a first expansion means connected to receive at least aportion of said cooled stream under pressure and expand it to a lowerpressure, whereby said stream is further cooled; and (c) a distillationcolumn connected to receive said further cooled stream, saiddistillation column being adapted to separate said further cooled streaminto an overhead vapor stream and said relatively less volatilefraction; the improvement wherein said apparatus includes (1) said firstcooling means being adapted to cool said gas stream under pressuresufficiently to partially condense it; (2) separating means connected tosaid first cooling means to receive said partially condensed gas streamand separate it into a vapor stream and at least one liquid stream; (3)first dividing means connected to said separating means to receive saidvapor stream and divide it into first and second streams; (4) firstcombining means connected to said first dividing means and saidseparating means to receive said first stream and at least a portion ofsaid at least one liquid stream and form a combined stream; (5) secondcooling means connected to said first combining means to receive saidcombined stream and cool it sufficiently to substantially condense it;(6) second expansion means connected to said second cooling means toreceive said substantially condensed combined stream and expand it tosaid lower pressure, said second expansion means being further connectedto said distillation column to supply said expanded cooled combinedstream to said distillation column at an upper mid-column feed position;(7) said first expansion means being connected to said first dividingmeans to receive said second stream and expand it to said lowerpressure, said first expansion means being further connected to saiddistillation column to supply said expanded second stream to saiddistillation column at a mid-column feed position below said uppermid-column feed position; (8) third expansion means being connected tosaid separating means to receive any remaining portion of said at leastone liquid stream and expand it to said lower pressure, said thirdexpansion means being further connected to said distillation column tosupply said expanded liquid stream to said distillation column at alower mid-column feed position below said mid-column feed position; (9)second dividing means connected to said distillation column to receivesaid overhead vapor stream separated therein and divide it into at leasta first portion and a second portion; (10) heat exchange means connectedto said second dividing means to receive at least a portion of saidsecond portion and heat it, thereafter discharging at least a portion ofsaid heated second portion as said volatile residue gas fraction; (11)vapor withdrawing means connected to said distillation column to receivea distillation vapor stream from a region of said distillation columnabove said upper mid-column feed position; (12) second combining meansconnected to said second dividing means and said vapor withdrawing meansto receive said first portion and said distillation vapor stream andform a combined vapor stream; (13) compressing means connected to saidsecond combining means to receive said combined vapor stream andcompress it to higher pressure; (14) said heat exchange means beingfurther connected to said compressing means to receive said compressedcombined vapor stream and cool it sufficiently to condense at least apart of it, thereby forming a condensed stream while supplying at leasta portion of the heating of step (10); (15) fourth expansion meansconnected to said heat exchange means to receive said condensed streamand expand it to said lower pressure, said fourth expansion means beingfurther connected to said distillation column to supply at least aportion of said expanded condensed stream to said distillation column ata top feed position; and (16) control means adapted to regulate thequantities and temperatures of said feed streams to said distillationcolumn to maintain the overhead temperature of said distillation columnat a temperature whereby the major portions of the components in saidrelatively less volatile fraction are recovered.
 20. In an apparatus forthe separation of a gas stream containing methane, C₂ components, C₃components, and heavier hydrocarbon components into a volatile residuegas fraction and a relatively less volatile fraction containing a majorportion of said C₂ components, C₃ components, and heavier hydrocarboncomponents or said C₃ components and heavier hydrocarbon components, insaid apparatus there being (a) a first cooling means to cool said gasstream under pressure connected to provide a cooled stream underpressure; (b) a first expansion means connected to receive at least aportion of said cooled stream under pressure and expand it to a lowerpressure, whereby said stream is further cooled; and (c) a distillationcolumn connected to receive said further cooled stream, saiddistillation column being adapted to separate said further cooled streaminto a first overhead vapor stream and said relatively less volatilefraction; the improvement wherein said apparatus includes (1) firstdividing means connected to said first cooling means to receive saidcooled stream and divide it into first and second streams; (2) secondcooling means connected to said first dividing means to receive saidfirst stream and cool it sufficiently to substantially condense it; (3)second expansion means connected to said second cooling means to receivesaid substantially condensed first stream and expand it to said lowerpressure, said second expansion means being further connected to acontacting and separating means to supply said expanded cooled firststream to said contacting and separating means at a mid-column feedposition, said contacting and separating means being adapted to producea second overhead vapor stream and a bottom liquid stream; (4) saidfirst expansion means being connected to said first dividing means toreceive said second stream and expand it to said lower pressure, saidfirst expansion means being further connected to said contacting andseparating means to supply said expanded second stream to saidcontacting and separating means at a first lower column feed positionbelow said mid-column feed position; (5) said distillation column beingconnected to said contacting and separating means to receive at least aportion of said bottom liquid stream; (6) said contacting and separatingmeans being further connected to said distillation column to receive atleast a portion of said first overhead vapor stream at a second lowercolumn feed position below said mid-column feed position; (7) seconddividing means connected to said contacting and separating means toreceive said second overhead vapor stream separated therein and divideit into at least a first portion and a second portion; (8) heat exchangemeans connected to said second dividing means to receive at least aportion of said second portion and heat it, thereafter discharging atleast a portion of said heated second portion as said volatile residuegas fraction; (9) vapor withdrawing means connected to said contactingand separating means to receive a distillation vapor stream from aregion of said contacting and separating device above said mid-columnfeed position; (10) combining means connected to said second dividingmeans and said vapor withdrawing means to receive said first portion andsaid distillation vapor stream and form a combined vapor stream; (11)compressing means connected to said combining means to receive saidcombined vapor stream and compress it to higher pressure; (12) said heatexchange means being further connected to said compressing means toreceive said compressed combined vapor stream and cool it sufficientlyto condense at least a part of it, thereby forming a condensed streamwhile supplying at least a portion of the heating of step (8); (13)third expansion means connected to said heat exchange means to receivesaid condensed stream and expand it to said lower pressure, said thirdexpansion means being further connected to said contacting andseparating means to supply at least a portion of said expanded condensedstream to said contacting and separating means at a top feed position;and (14) control means adapted to regulate the quantities andtemperatures of said feed streams to said contacting and separatingmeans to maintain the overhead temperature of said contacting andseparating means at a temperature whereby the major portions of thecomponents in said relatively less volatile fraction are recovered. 21.In an apparatus for the separation of a gas stream containing methane,C₂ components, C₃ components, and heavier hydrocarbon components into avolatile residue gas fraction and a relatively less volatile fractioncontaining a major portion of said C₂ components, C₃ components, andheavier hydrocarbon components or said C₃ components and heavierhydrocarbon components, in said apparatus there being (a) a firstcooling means to cool said gas stream under pressure connected toprovide a cooled stream under pressure; (b) a first expansion meansconnected to receive at least a portion of said cooled stream underpressure and expand it to a lower pressure, whereby said stream isfurther cooled; and (c) a distillation column connected to receive saidfurther cooled stream, said distillation column being adapted toseparate said further cooled stream into a first overhead vapor streamand said relatively less volatile fraction; the improvement wherein saidapparatus includes (1) first dividing means prior to said first coolingmeans to divide said gas stream into first and second streams; (2)second cooling means connected to said first dividing means to receivesaid first stream and cool it sufficiently to substantially condense it;(3) second expansion means connected to said second cooling means toreceive said substantially condensed first stream and expand it to saidlower pressure, said second expansion means being further connected to acontacting and separating means to supply said expanded cooled firststream to said contacting and separating means at a mid-column feedposition, said contacting and separating means being adapted to producea second overhead vapor stream and a bottom liquid stream; (4) saidfirst cooling means being connected to said first dividing means toreceive said second stream and cool it; (5) said first expansion meansbeing connected to said first cooling means to receive said cooledsecond stream and expand it to said lower pressure, said first expansionmeans being further connected to said contacting and separating means tosupply said expanded cooled second stream to said contacting andseparating means at a first lower column feed position below saidmid-column feed position; (6) said distillation column being connectedto said contacting and separating means to receive at least a portion ofsaid bottom liquid stream; (7) said contacting and separating meansbeing further connected to said distillation column to receive at leasta portion of said first overhead vapor stream at a second lower columnfeed position below said mid-column feed position; (8) second dividingmeans connected to said contacting and separating means to receive saidsecond overhead vapor stream separated therein and divide it into atleast a first portion and a second portion; (9) heat exchange meansconnected to said second dividing means to receive at least a portion ofsaid second portion and heat it, thereafter discharging at least aportion of said heated second portion as said volatile residue gasfraction; (10) vapor withdrawing means connected to said contacting andseparating means to receive a distillation vapor stream from a region ofsaid contacting and separating device above said mid-column feedposition; (11) combining means connected to said second dividing meansand said vapor withdrawing means to receive said first portion and saiddistillation vapor stream and form a combined vapor stream; (12)compressing means connected to said combining means to receive saidcombined vapor stream and compress it to higher pressure; (13) said heatexchange means being further connected to said compressing means toreceive said compressed combined vapor stream and cool it sufficientlyto condense at least a part of it, thereby forming a condensed streamwhile supplying at least a portion of the heating of step (9); (14)third expansion means connected to said heat exchange means to receivesaid condensed stream and expand it to said lower pressure, said thirdexpansion means being further connected to said contacting andseparating means to supply at least a portion of said expanded condensedstream to said contacting and separating means at a top feed position;and (15) control means adapted to regulate the quantities andtemperatures of said feed streams to said contacting and separatingmeans to maintain the overhead temperature of said contacting andseparating means at a temperature whereby the major portions of thecomponents in said relatively less volatile fraction are recovered. 22.In an apparatus for the separation of a gas stream containing methane,C₂ components, C₃ components, and heavier hydrocarbon components into avolatile residue gas fraction and a relatively less volatile fractioncontaining a major portion of said C₂ components, C₃ components, andheavier hydrocarbon components or said C₃ components and heavierhydrocarbon components, in said apparatus there being (a) a firstcooling means to cool said gas stream under pressure connected toprovide a cooled stream under pressure; (b) a first expansion meansconnected to receive at least a portion of said cooled stream underpressure and expand it to a lower pressure, whereby said stream isfurther cooled; and (c) a distillation column connected to receive saidfurther cooled stream, said distillation column being adapted toseparate said further cooled stream into a first overhead vapor streamand said relatively less volatile fraction; the improvement wherein saidapparatus includes (1) said first cooling means being adapted to coolsaid gas stream under pressure sufficiently to partially condense it;(2) separating means connected to said first cooling means to receivesaid partially condensed gas stream and separate it into a vapor streamand at least one liquid stream; (3) first dividing means connected tosaid separating means to receive said vapor stream and divide it intofirst and second streams; (4) second cooling means connected to saidfirst dividing means to receive said first stream and cool itsufficiently to substantially condense it; (5) second expansion meansconnected to said second cooling means to receive said substantiallycondensed first stream and expand it to said lower pressure, said secondexpansion means being further connected to a contacting and separatingmeans to supply said expanded cooled first stream to said contacting andseparating means at a mid-column feed position, said contacting andseparating means being adapted to produce a second overhead vapor streamand a bottom liquid stream; (6) said first expansion means beingconnected to said first dividing means to receive said second stream andexpand it to said lower pressure, said first expansion means beingfurther connected to said contacting and separating means to supply saidexpanded second stream to said contacting and separating means at afirst lower column feed position below said mid-column feed position;(7) third expansion means connected to said separating means to receiveat least a portion of said at least one liquid stream and expand it tosaid lower pressure, said third expansion means being further connectedto said distillation column to supply said expanded liquid stream tosaid distillation column at a mid-column feed position; (8) saiddistillation column being connected to said contacting and separatingmeans to receive at least a portion of said bottom liquid stream; (9)said contacting and separating means being further connected to saiddistillation column to receive at least a portion of said first overheadvapor stream at a second lower column feed position below saidmid-column feed position; (10) second dividing means connected to saidcontacting and separating means to receive said second overhead vaporstream separated therein and divide it into at least a first portion anda second portion; (11) heat exchange means connected to said seconddividing means to receive at least a portion of said second portion andheat it, thereafter discharging at least a portion of said heated secondportion as said volatile residue gas fraction; (12) vapor withdrawingmeans connected to said contacting and separating means to receive adistillation vapor stream from a region of said contacting andseparating device above said mid-column feed position; (13) combiningmeans connected to said second dividing means and said vapor withdrawingmeans to receive said first portion and said distillation vapor streamand form a combined vapor stream; (14) compressing means connected tosaid combining means to receive said combined vapor stream and compressit to higher pressure; (15) said heat exchange means being furtherconnected to said compressing means to receive said compressed combinedvapor stream and cool it sufficiently to condense at least a part of it,thereby forming a condensed stream while supplying at least a portion ofthe heating of step (11); (16) fourth expansion means connected to saidheat exchange means to receive said condensed stream and expand it tosaid lower pressure, said fourth expansion means being further connectedto said contacting and separating means to supply at least a portion ofsaid expanded condensed stream to said contacting and separating meansat a top feed position; and (17) control means adapted to regulate thequantities and temperatures of said feed streams to said contacting andseparating means to maintain the overhead temperature of said contactingand separating means at a temperature whereby the major portions of thecomponents in said relatively less volatile fraction are recovered. 23.In an apparatus for the separation of a gas stream containing methane,C₂ components, C₃ components, and heavier hydrocarbon components into avolatile residue gas fraction and a relatively less volatile fractioncontaining a major portion of said C₂ components, C₃ components, andheavier hydrocarbon components or said C₃ components and heavierhydrocarbon components, in said apparatus there being (a) a firstcooling means to cool said gas stream under pressure connected toprovide a cooled stream under pressure; (b) a first expansion meansconnected to receive at least a portion of said cooled stream underpressure and expand it to a lower pressure, whereby said stream isfurther cooled; and (c) a distillation column connected to receive saidfurther cooled stream, said distillation column being adapted toseparate said further cooled stream into a first overhead vapor streamand said relatively less volatile fraction; the improvement wherein saidapparatus includes (1) first dividing means prior to said first coolingmeans to divide said gas stream into first and second streams; (2)second cooling means connected to said first dividing means to receivesaid first stream and cool it sufficiently to substantially condense it;(3) second expansion means connected to said second cooling means toreceive said substantially condensed first stream and expand it to saidlower pressure, said second expansion means being further connected to acontacting and separating means to supply said expanded cooled firststream to said contacting and separating means at a mid-column feedposition, said contacting and separating means being adapted to producea second overhead vapor stream and a bottom liquid stream; (4) saidfirst cooling means being connected to said first dividing means toreceive said second stream, said first cooling means being adapted tocool said second stream under pressure sufficiently to partiallycondense it; (5) separating means connected to said first cooling meansto receive said partially condensed second stream and separate it into avapor stream and at least one liquid stream; (6) said first expansionmeans being connected to said separating means to receive said vaporstream and expand it to said lower pressure, said first expansion meansbeing further connected to said contacting and separating means tosupply said expanded vapor stream to said contacting and separatingmeans at a first lower column feed position below said mid-column feedposition; (7) third expansion means connected to said separating meansto receive at least a portion of said at least one liquid stream andexpand it to said lower pressure, said third expansion means beingfurther connected to said distillation column to supply said expandedliquid stream to said distillation column at a mid-column feed position;(8) said distillation column being connected to said contacting andseparating means to receive at least a portion of said bottom liquidstream; (9) said contacting and separating means being further connectedto said distillation column to receive at least a portion of said firstoverhead vapor stream at a second lower column feed position below saidmid-column feed position; (10) second dividing means connected to saidcontacting and separating means to receive said second overhead vaporstream separated therein and divide it into at least a first portion anda second portion; (11) heat exchange means connected to said seconddividing means to receive at least a portion of said second portion andheat it, thereafter discharging at least a portion of said heated secondportion as said volatile residue gas fraction; (12) vapor withdrawingmeans connected to said contacting and separating means to receive adistillation vapor stream from a region of said contacting andseparating device above said mid-column feed position; (13) combiningmeans connected to said second dividing means and said vapor withdrawingmeans to receive said first portion and said distillation vapor streamand form a combined vapor stream; (14) compressing means connected tosaid combining means to receive said combined vapor stream and compressit to higher pressure; (15) said heat exchange means being furtherconnected to said compressing means to receive said compressed combinedvapor stream and cool it sufficiently to condense at least a part of it,thereby forming a condensed stream while supplying at least a portion ofthe heating of step (11); (16) fourth expansion means connected to saidheat exchange means to receive said condensed stream and expand it tosaid lower pressure, said fourth expansion means being further connectedto said contacting and separating means to supply at least a portion ofsaid expanded condensed stream to said contacting and separating meansat a top feed position; and (17) control means adapted to regulate thequantities and temperatures of said feed streams to said contacting andseparating means to maintain the overhead temperature of said contactingand separating means at a temperature whereby the major portions of thecomponents in said relatively less volatile fraction are recovered. 24.In an apparatus for the separation of a gas stream containing methane,C₂ components, C₃ components, and heavier hydrocarbon components into avolatile residue gas fraction and a relatively less volatile fractioncontaining a major portion of said C₂ components, C₃ components, andheavier hydrocarbon components or said C₃ components and heavierhydrocarbon components, in said apparatus there being (a) a firstcooling means to cool said gas stream under pressure connected toprovide a cooled stream under pressure; (b) a first expansion meansconnected to receive at least a portion of said cooled stream underpressure and expand it to a lower pressure, whereby said stream isfurther cooled; and (c) a distillation column connected to receive saidfurther cooled stream, said distillation column being adapted toseparate said further cooled stream into a first overhead vapor streamand said relatively less volatile fraction; the improvement wherein saidapparatus includes (1) said first cooling means being adapted to coolsaid gas stream under pressure sufficiently to partially condense it;(2) separating means connected to said first cooling means to receivesaid partially condensed gas stream and separate it into a vapor streamand at least one liquid stream; (3) first dividing means connected tosaid separating means to receive said vapor stream and divide it intofirst and second streams; (4) first combining means connected to saidfirst dividing means and said separating means to receive said firststream and at least a portion of said at least one liquid stream andform a combined stream; (5) second cooling means connected to said firstcombining means to receive said combined stream and cool it sufficientlyto substantially condense it; (6) second expansion means connected tosaid second cooling means to receive said substantially condensedcombined stream and expand it to said lower pressure, said secondexpansion means being further connected to a contacting and separatingmeans to supply said expanded cooled combined stream to said contactingand separating means at a mid-column feed position, said contacting andseparating means being adapted to produce a second overhead vapor streamand a bottom liquid stream; (7) said first expansion means beingconnected to said first dividing means to receive said second stream andexpand it to said lower pressure, said first expansion means beingfurther connected to said contacting and separating means to supply saidexpanded second stream to said contacting and separating means at afirst lower column feed position below said mid-column feed position;(8) third expansion means connected to said separating means to receiveany remaining portion of said at least one liquid stream and expand itto said lower pressure, said third expansion means being furtherconnected to said distillation column to supply said expanded liquidstream to said distillation column at a mid-column feed position; (9)said distillation column being connected to said contacting andseparating means to receive at least a portion of said bottom liquidstream; (10) said contacting and separating means being furtherconnected to said distillation column to receive at least a portion ofsaid first overhead vapor stream at a second lower column feed positionbelow said mid-column feed position; (11) second dividing meansconnected to said contacting and separating means to receive said secondoverhead vapor stream separated therein and divide it into at least afirst portion and a second portion; (12) heat exchange means connectedto said second dividing means to receive at least a portion of saidsecond portion and heat it, thereafter discharging at least a portion ofsaid heated second portion as said volatile residue gas fraction; (13)vapor withdrawing means connected to said contacting and separatingmeans to receive a distillation vapor stream from a region of saidcontacting and separating device above said mid-column feed position;(14) second combining means connected to said second dividing means andsaid vapor withdrawing means to receive said first portion and saiddistillation vapor stream and form a combined vapor stream; (15)compressing means connected to said second combining means to receivesaid combined vapor stream and compress it to higher pressure; (16) saidheat exchange means being further connected to said compressing means toreceive said compressed combined vapor stream and cool it sufficientlyto condense at least a part of it, thereby forming a condensed streamwhile supplying at least a portion of the heating of step (12); (17)fourth expansion means connected to said heat exchange means to receivesaid condensed stream and expand it to said lower pressure, said fourthexpansion means being further connected to said contacting andseparating means to supply at least a portion of said expanded condensedstream to said contacting and separating means at a top feed position;and (18) control means adapted to regulate the quantities andtemperatures of said feed streams to said contacting and separatingmeans to maintain the overhead temperature of said contacting andseparating means at a temperature whereby the major portions of thecomponents in said relatively less volatile fraction are recovered. 25.The improvement according to claim 15, 16, 17, 18, or 19 wherein saidvapor withdrawing means is connected to said distillation column toreceive said distillation vapor stream from a region of saiddistillation column below said upper mid-column feed position and abovesaid mid-column feed position.
 26. The improvement according to claim15, 16, 17, 18, or 19 wherein said vapor withdrawing means is connectedto said distillation column to receive said distillation vapor streamfrom a region of said distillation column below said mid-column feedposition.
 27. The improvement according to claim 20, 21, 22, 23, or 24wherein said vapor withdrawing means is connected to said contacting andseparating means to receive said distillation vapor stream from a regionof said contacting and separating means below said mid-column feedposition and above said first and second lower column feed positions.28. The improvement according to claim 20, 21, 22, or 23 wherein (1) athird dividing means is connected to said distillation column to receivesaid first overhead vapor stream and divide it into said distillationvapor stream and a second distillation vapor stream; (2) said contactingand separating device is adapted to be connected to said third dividingmeans to receive said second distillation vapor stream at said secondlower column feed position; and (3) said combining means is adapted tobe connected to said third dividing means to receive said distillationvapor stream.
 29. The improvement according to claim 24 wherein (1) athird dividing means is connected to said distillation column to receivesaid first overhead vapor stream and divide it into said distillationvapor stream and a second distillation vapor stream; (2) said contactingand separating device is adapted to be connected to said third dividingmeans to receive said second distillation vapor stream at said secondlower column feed position; and (3) said second combining means isadapted to be connected to said third dividing means to receive saiddistillation vapor stream.